1. Field of the Invention
The present invention relates to a system for protecting an Insulated Gate Bipolar Transistor (IGBT) against faults such as a short-circuit fault and a fault under load.
2. Description of the Related Art
Devices for power control and conversion use power transistors. It is possible to accomplish power control or conversion by switching on or off such power control transistors at predetermined intervals. These elements are selected so as to reliably handle circuit currents not only under normal conditions but also under overload conditions. However, the elements may be affected by very high surge currents under fault conditions such as a short-circuit fault or a Fault Under Load (FUL). To prevent this, it is necessary to properly control and remove fault currents.
Especially in the case of an IGBT power transistor, currents 10 times higher than the rated level of the transistor may flow in it under serious fault conditions. To prevent high power loss and destruction of the IGBT caused by such short-circuit currents, appropriate fault correction must be performed in a short time such as microseconds. A number of approaches have been suggested to protect the IGBT. For example, typical methods use a sensing IGBT, an emitter resistor, and a high voltage diode. Although these methods are widely used currently, it is not easy to integrate the high power elements, the sensing IGBT, and the like into a gate drive integrated circuit.